Kill a rat
Just start up Jewellery Store, go to the back alley and shoot one of the rats running around.

Trigger the alarm after opening the vault
Choose any Map that you are capable to complete in stealth. Complete it, but before hitting the big red button, shoot a few times in the air with a non-silenced gun. If you don't have one, just run into the building and let yourself be seen. Once you can hear the alarm blaring, you can leave.

Get a powerbox sabotaged by a powerbox defuser
Go loud on any map, start the first powerbox and do not kill any defuser.

Walk into barbed wire placed by an interceptor
Play any map loud, wait for an interceptor to show up. Once you see one, do not kill him, as soon as he places some barbed wire down, just walk through it.

Get blinded by a blinding shield
Play any map loud and wait for a blinding shield to show up. You can easily recognize it by its sound. Get flashed by it.

Blow yourself up with a C4
Reach lvl 26 and buy the C4, or get someone who already owns it. Start round, through C4, get blown up.